The present invention relates to a processing station for charging, exposing and developing printing masters, comprising an exposure table, at least one corona device, a developing unit and an optical scanning-exposure device.
The production of lettered and imaged printing plates in a processing unit is carried out in such a manner that the printing plates are first electrostatically charged and then an original is projected imagewise upon the plate. After this exposing procedure, the printing plate is developed with a developer, fixed and decoated. It is then ready for use on a printing press.
German Pat. No. 2,462,216 discloses an apparatus for the manufacture of printing plates by electrophotographic means, in which an individual printing plate is picked up from a stack in a plate holder by a transport device comprising a transport carriage with reduced pressure suction means. The transport carriage transfers the printing plate to an exposure platform. Charging of the individual printing plate and transporting it to the exposure platform are combined in a time-saving manner by mounting at the front of the transport carriage a corona charging station for the electrostatic charging of the printing plates. The corona charging station extends transversely to the direction of movement of the carriage which runs on two guide rails and is driven by a motor mounted on top. The carriage has a vacuum plate which is attached to its underside and which is, by a number of holes, connected with a vacuum pump. When the transport carriage is placed on top of the uppermost printing plate in the plate holder, reduced pressure is generated by which the printing plate is drawn by suction to the vacuum plate. By means of the motor, the transport carriage is then displaced in the direction of the exposure platform. As soon as the carriage has reached its position above the exposure platform, it is lowered, and the vacuum in the vacuum plate is released so that the printing plate is set free and is deposited on the exposure platform. The exposure platform is also designed as a vacuum plate and is subjected to reduced pressure, and as a result the printing plate is firmly held against the platform. After depositing the printing plate on the exposure platform, the transport carriage returns to its initial position above the plate holder.
U.S. Pat. No. 4,149,798 discloses a transport station for printing plates, which includes a stacking area containing a supply of printing plates. Printing plates are transported from the stacking area to a conveyor by means of a control mechanism which is provided with a number of suction cups. The conveyor transfers the printing plates to an exposure platform which has a plurality of holes on its upper surface and forms a chamber connected to a vacuum pump by a vacuum line. When the printing plate has assumed a predetermined position on the surface of the exposure platform, a vacuum is drawn, and the printing plate is held on the platform for exposure by means of an exposing system. The exposing system comprises a movable carriage as well as a corona charging device and a light-reflecting mirror mounted on the carriage. A laser which radiates modulated laser light is positioned in such a way that the emitted light beam is deflected by the mirror and impinges on the printing plate lying on the exposure platform, in a plane which is approximately normal to the plate surface.
In the prior art devices, the individual processing stages of a printing plate, such as charging, exposing and developing, proceed in chronological order in separate processing stations. A fresh printing plate can usually only be fed in, when the preceding plate has reached the fixing station or is leaving the fixing station. An additional delay is caused by the fact that a printing plate positioned on the exposure platform is only exposed during the forward travel of an optical scanning and recording device equipped with lasers and an appurtenant laser optical system, whereas processing does not take place while the scanning device travels backwards. That is to say that before another processing cycle for a printing plate can be started, the scanning device must return to its initial position.